The exemplary embodiments relate generally to gas turbine engines and more particularly, to valve assemblies used to regulate fluid flow for gas turbine engines.
Gas turbine engines typically include a compressor, a combustor, and at least one turbine. The compressor may compress air, which may be mixed with fuel and channeled to the combustor. The mixture may then be ignited for generating hot combustion gases, and the combustion gases may be channeled to the turbine. The turbine may extract energy from the combustion gases for powering the compressor, as well as producing useful work to propel an aircraft in flight or to power a load, such as an electrical generator.
Gas turbine engines typically include an engine casing that extends circumferentially around the compressor and turbine. Within at least some known engines, a plurality of ducts and valves coupled to an exterior surface of the casing are used to channel fluid flow from one area of the engine for use within another area of the engine or for exhausting overboard. For example, such ducts and valves may form a portion of an environmental control system (ECS).
At least some known valve assemblies are used to control fluid flow that is at a high temperature and/or high pressure. Such valve assemblies include a substantially cylindrical valve body that is coupled between adjacent sections of ducting. The valve body includes a valve sealing mechanism that is selectively positionable to control fluid flow through the valve. More specifically, at least some known valves include a piston/cylinder arrangement that is positioned external to the valve body and is coupled to the valve sealing mechanism to provide the motive force necessary to selectively position the valve sealing mechanism.
Because the piston/cylinder arrangement is offset from the main valve body, a center of gravity of the valve assembly is typically displaced a distance from a centerline axis of the valve body. Such an eccentric center of gravity may induce bending stresses into the valve assembly, adjoining tubing, and supporting brackets during engine operation. Depending on the application, the physical size and weight of the piston/cylinder arrangement may also present difficulties during the duct routing phase of the engine design.
Some known valve assemblies have attempted to overcome these issues by including a bend in the ducting leading to the valve sealing mechanism. The intent of this change was to orient the valve sealing mechanism to be perpendicular to the piston and to orient the force transfer pins to be perpendicular to the piston travel direction. However, this design requires the use of a wishbone arrangement intermediate between the piston and the valve sealing mechanism. The wishbone could cause vibration modes with resultant unacceptable linkage wear issues or part stresses. The wishbone also included slots for the connection pins, which could allow dirt and moisture to enter the actuator cavity.